Magnetic disk device

Abstract

To provide a magnetic disk device that can measure PPO correction values with high efficiency.SOLUTION: A plurality of first positions are set in a radial direction of a magnetic disk. The plurality of first positions includes a plurality of second positions and a third position different from the plurality of second positions. A controller of the magnetic disk device measures a RRO (Repeatable RunOut) correction value for each of the plurality of second positions, and executes a first step in which a RRO correction value is not measured for the third position. After the first step, the controller executes a second step in which write or read access is performed on a plurality of tracks. The second step includes acquiring a position error signal by a read head during access and calculating the RRO correction value for the third position based on the position error signal.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This embodiment relates to a magnetic disk device. [Background technology]

[0002] Repeatable Runout (RRO) has been known as one of the components of magnetic head positioning error in magnetic disk drives. RRO is the deviation between the track trajectory defined by the burst pattern and the actual track trajectory. RRO fluctuates in synchronization with the rotation of the magnetic disk (and spindle motor).

[0003] During the manufacturing process of a magnetic disk drive, correction values ​​(hereinafter referred to as RRO correction values) for correcting misalignment due to RRO are measured at multiple radial positions. The obtained RRO correction values ​​are stored in a non-volatile memory area as additional information to the servo data. When the magnetic disk drive is used, the RRO correction values ​​are used to correct the position of the magnetic head. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 1,179,0949 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of one embodiment is to provide a magnetic disk drive that can measure an RRO correction value with high efficiency. [Means for solving the problem]

[0006] According to one embodiment, a magnetic disk drive includes a magnetic disk, a magnetic head, and a controller. A plurality of first positions for measuring RRO correction values ​​are set in the radial direction of the magnetic disk. The plurality of first positions include a plurality of second positions and a plurality of third positions different from the second positions. A plurality of tracks are provided on the magnetic disk. The magnetic head includes a write head for performing write access to the magnetic disk and a read head for performing read access to the magnetic disk. The controller executes a first step of measuring an RRO correction value for each of the plurality of second positions and not measuring an RRO correction value for the third position. Measuring the RRO correction value for each of the plurality of second positions includes moving the magnetic head so that the read head is positioned at a fourth position, which is one of the plurality of second positions, for each of the plurality of second positions; acquiring a first position error signal by the read head while maintaining the read head over the fourth position; and calculating an RRO correction value at the fourth position based on the first position error signal. After the first step, the controller executes a second step of performing write or read access to the plurality of tracks. The second step includes acquiring a second position error signal by the read head during the access, and calculating an RRO correction value for a third position based on the second position error signal. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a magnetic disk device according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a magnetic disk according to the embodiment. [Figure 3] FIG. 3 is a diagram illustrating an example of the positional relationship between the read head and the write head according to the embodiment. [Figure 4] FIG. 4 is a diagram for explaining that the head position distance in the embodiment differs depending on the position of the magnetic head. [Figure 5] FIG. 5 is a diagram for explaining a plurality of measurement positions and a specific measurement position according to the embodiment. [Figure 6] FIG. 6 is a diagram illustrating an example of information recorded in the read head position table according to the embodiment. [Figure 7] FIG. 7 is a flowchart showing an example of an operation in a manufacturing process executed by the magnetic disk device according to the embodiment. [Figure 8] FIG. 8 is a flowchart illustrating an example of an operation in an RRO learning process of the magnetic disk device according to the embodiment. [Figure 9] FIG. 9 is a flowchart illustrating an example of the operation of the write-all process of the magnetic disk device according to the embodiment. [Figure 10] FIG. 10 is a flowchart showing an example of the operation in the read-all process of the magnetic disk device according to the embodiment. [Figure 11] FIG. 11 is a diagram for explaining a method for estimating an RRO correction value at a specific measurement position in a write-all process and a read-all process in a magnetic disk device according to an embodiment. [Figure 12] FIG. 12 is a diagram for explaining another example of the arrangement of a plurality of measurement positions according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A magnetic disk drive according to an embodiment will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to this embodiment.

[0009] (Embodiment) FIG. 1 is a diagram illustrating an example of the configuration of a magnetic disk device 1 according to an embodiment.

[0010] The magnetic disk device 1 is connected to a host 2. The magnetic disk device 1 can receive access commands, such as write commands or read commands, from the host 2.

[0011] The magnetic disk device 1 includes a magnetic disk 11 having a magnetic layer formed on its surface. The magnetic disk device 1 accesses the magnetic disk 11 in response to an access command. The access includes writing data and reading data.

[0012] Data is written and read by a magnetic head 22. Specifically, in addition to a magnetic disk 11, the magnetic disk device 1 includes a spindle motor (SPM) 12, a ramp 13, an actuator arm 15, a voice coil motor (VCM) 16, a servo controller (SVC) 21, the magnetic head 22, a hard disk controller (HDC) 23, a preamplifier 24, a read / write channel (RWC) 25, a processor 26, a flash read only memory (FROM) 28, and a dynamic random access memory (DRAM) 29.

[0013] The magnetic disk 11 is rotated at a predetermined rotational speed by the SPM 12 attached coaxially.

[0014] The SVC 21 is an integrated circuit that functions as a driver for driving the SPM 12 and the VCM 16. The processor 26 controls the rotation of the SPM 12 and the VCM 16 via the SVC 21.

[0015] The magnetic head 22 includes a write head 22w and a read head 22r. The magnetic head 22 writes data to the magnetic disk 11 using the write head 22w. The magnetic head 22 reads data from the magnetic disk 11 using the read head 22r. The magnetic head 22 is attached to the tip of the actuator arm 15. The magnetic head 22 is moved in the radial direction of the magnetic disk 11 by the VCM 16, which is driven by the SVC 21. Note that a plurality of write heads 22w and / or read heads 22r provided on the magnetic head 22 may be provided for a single magnetic head 22.

[0016] When the magnetic disk 11 is stopped from rotating, the magnetic head 22 is moved onto the ramp 13. The ramp 13 is configured to hold the magnetic head 22 at a position spaced apart from the magnetic disk 11.

[0017] The preamplifier 24 is an integrated circuit that writes and reads data via the magnetic head 22. During a read operation, the preamplifier 24 amplifies and outputs a signal read from the magnetic disk 11 by the magnetic head 22, and supplies the signal to the RWC 25. During a write operation, the preamplifier 24 amplifies a signal corresponding to the data to be written, which is supplied from the RWC 25, and supplies the signal to the magnetic head 22.

[0018] The HDC 23 controls the transmission and reception of data to and from the host 2 via the I / F bus, and controls the DRAM 29 .

[0019] The DRAM 29 is used as a buffer for data sent and received between the host 2. For example, the DRAM 29 is used to temporarily store data to be written or data read from the magnetic disk 11.

[0020] The DRAM 29 is also used as an operating memory by the processor 26. The DRAM 29 is used as an area into which firmware programs are loaded and an area in which various management data are temporarily stored.

[0021] The RWC 25 modulates the data to be written, which is supplied from the HDC 23, and supplies the modulated data to the preamplifier 24. The RWC 25 also performs demodulation, including error correction, on the signal read from the magnetic disk 11 and supplied from the preamplifier 24, and then outputs the signal to the HDC 23 as digital data.

[0022] The processor 26 is, for example, a CPU (Central Processing Unit). A FROM (Flash Read Only Memory) 28 and a DRAM 29 are connected to the processor 26.

[0023] The FROM 28 stores a firmware program and various setting information, etc. The firmware program may be stored on the magnetic disk 11.

[0024] The processor 26 performs overall control of the magnetic disk device 1 in accordance with a firmware program stored in the FROM 28 or the magnetic disk 11. For example, the processor 26 loads the firmware program from the FROM 28 or the magnetic disk 11 into the DRAM 29, and controls the SVC 21, the preamplifier 24, the RWC 25, the HDC 23, etc. in accordance with the firmware program loaded into the DRAM 29.

[0025] Note that some or all of the functions of the processor 26 may be realized by a hardware circuit such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

[0026] The HDC 23, RWC 25, and processor 26 are configured as a single integrated circuit, a System-On-a-Chip (SoC) 30. The SoC 30 may also include other elements (e.g., a FROM 28 or a DRAM 29). The SoC 30 is an example of a controller.

[0027] 2 is a diagram showing an example of the configuration of the magnetic disk 11 according to the embodiment. Note that this diagram shows an example of the rotation direction of the magnetic disk 11. The magnetic head 22 moves relative to the magnetic disk 11 as the magnetic disk 11 rotates. Therefore, the write / read direction, i.e., the direction in which data is written or read by the magnetic head 22 along the circumferential direction, is opposite to the rotation direction of the magnetic disk 11.

[0028] In the radial direction, the direction from the edge of the magnetic disk 11 to the center is the inner diameter (ID) direction, and the direction from the center of the magnetic disk 11 to the edge is the outer diameter (OD) direction.

[0029] During the manufacturing process, servo data used to position the magnetic head 22 is written on the magnetic disk 11 by, for example, a servo writer or self-servo writing (SSW). As shown in Fig. 2, as an example of the arrangement of servo areas where servo data is written, a plurality of servo areas SV are formed, arranged radially in the radial direction and at predetermined intervals in the circumferential direction. A data area DA, where data is written, is arranged between two consecutive servo areas SV in the circumferential direction.

[0030] A plurality of concentric servo tracks 41 are provided in the radial direction of the magnetic disk 11. Servo data written in the servo areas SV is used to position the magnetic head 22.

[0031] More specifically, a plurality of concentric data tracks are provided on the magnetic disk 11 in an area where a plurality of servo tracks 41 are provided. The plurality of servo tracks 41 may be used as a plurality of data tracks, or a plurality of data tracks different from the plurality of servo tracks 41 may be provided. A plurality of data sectors are arranged in the circumferential direction in an area divided by the data areas DA on each data track. Data can be written to each data sector by the magnetic head 22. The data that can be written to each data sector includes user data received from the host 2, metadata (e.g., error correction code) associated with the user data, system data, etc. The magnetic disk device 1 stores in advance settings for the positional relationship between the plurality of servo tracks 41 and the plurality of data tracks. The magnetic disk device 1 performs positioning control to position the magnetic head 22 on a target data track based on the servo data recorded in the servo areas SV. The positioning control includes a seek operation, which is an operation to move the magnetic head 22 radially toward the target data track, and a tracking operation to maintain the magnetic head 22 on the target data track.

[0032] The plurality of data tracks is an example of a plurality of tracks.

[0033] The servo data includes sector / cylinder information, burst patterns, and RRO correction values. The sector / cylinder information indicates the servo addresses (servo sector addresses) in the circumferential direction of the magnetic disk 11 and the track positions (track numbers) set in the radial direction. The track numbers obtained from the sector / cylinder information are integer values, and the burst patterns indicate the offset amount after the decimal point based on the track number.

[0034] The ideal track shape is a perfect circle. However, due to vibrations and other factors received when writing servo data, distortions occur in the servo track 41. Therefore, the radial position (radial position) determined based on the burst pattern (more precisely, the combination of sector / cylinder information and the burst pattern) may deviate from the ideal radial position. This positional deviation contributes to a deterioration in positioning accuracy. This positional deviation occurs repeatedly and in the same manner with each rotation of the magnetic disk (and spindle motor), and is therefore called RRO. During the manufacturing process, RRO correction values ​​are learned at multiple radial positions. Then, during use of the magnetic disk device 1, control is executed to cancel the positional deviation due to RRO based on the RRO correction value when positioning the magnetic head 22 over the target track.

[0035] The location where the RRO correction values ​​obtained at multiple radial positions are stored does not necessarily have to be the servo area SV, as long as it is a nonvolatile storage area. The RRO correction values ​​may be stored in the data area DA or in a nonvolatile memory such as the FROM 28. The magnetic disk device 1 reads the RRO correction values ​​from the nonvolatile storage area and corrects the position of the magnetic head 22 using the RRO correction values ​​obtained by reading.

[0036] Hereinafter, the process of measuring RRO correction values ​​at multiple radial positions will be referred to as the RRO learning process. Each radial position where the RRO correction value is measured will be referred to as a measurement position or an RRO measurement position. Correction of the positional deviation due to RRO will be referred to as RRO correction.

[0037] The multiple measurement positions can be set regardless of the arrangement of the data tracks. When a target data track is located at a radial position between two adjacent measurement positions, the SoC 30 performs RRO correction as follows: The SoC 30 estimates an RRO correction value at the radial position of the target data track by interpolating multiple RRO correction values, including the RRO correction values ​​at the two measurement positions. The SoC 30 then performs RRO correction using the estimated RRO correction value.

[0038] The interpolation may be a linear interpolation using the RRO correction values ​​of two measurement positions adjacent to the target data track, or a polynomial interpolation of second or higher order using the RRO correction values ​​of three or more measurement positions including the two measurement positions.

[0039] To maximize positioning accuracy, multiple measurement positions are set at as small an interval as possible in the radial direction. Measuring the RRO correction value at one measurement position involves measuring a position error signal at that measurement position and calculating an RRO correction value based on the measured position error signal. Because multiple measurement positions are set and RRO correction values ​​are measured at all of these measurement positions, the RRO learning process takes a significant amount of time.

[0040] In an embodiment, in order to reduce the time required to measure the RRO correction values ​​at all measurement positions, the SoC 30 is configured to skip measuring the RRO correction values ​​at some measurement positions in the RRO learning process.

[0041] The manufacturing process includes, after the RRO learning process, a process of writing data to all data tracks of the magnetic disk 11 and reading data from all data tracks of the magnetic disk 11. The operation of writing data to all data tracks of the magnetic disk 11 is referred to as a write-all process. The operation of reading data from all data tracks of the magnetic disk 11 is referred to as a read-all process. The pair of the write-all process and the read-all process is executed to detect defective data sectors and verify whether each data sector can be accessed normally. The pair of the write-all process and the read-all process may be executed multiple times. The manufacturing process may include a process of detecting defective data sectors and a process of detecting defective servo sectors in addition to the write-all process and the read-all process.

[0042] The multiple measurement positions may include a radial position accessed in a write-all process or a read-all process. Such a radial position among the multiple measurement positions accessed in a write-all process or a read-all process is referred to as a specific measurement position. If the multiple measurement positions include a radial position accessed in a process of detecting defective data sectors or defective servo sectors, that radial position may be considered a specific measurement position.

[0043] In the RRO learning process, the SoC 30 skips measuring the RRO correction value at a specific measurement position. Then, when the SoC 30 accesses a specific measurement position or a location near the specific measurement position in the write-all process or read-all process after the RRO learning process, the SoC 30 measures the RRO correction value at the specific measurement position. Therefore, in the RRO learning process, the seek operation of the magnetic head 22 and the tracking operation for one revolution of the data track are omitted for each specific measurement position, thereby reducing the time required to measure the RRO correction value at all measurement positions. In other words, the efficiency of measuring the RRO correction value is improved.

[0044] Before describing the multiple measurement positions and the specific measurement position in detail, the radial positions through which the read head 22r passes and the radial positions through which the write head 22w passes will be described.

[0045] 3 is a diagram illustrating an example of the positional relationship between the read head 22r and the write head 22w according to the embodiment. According to the example shown in this figure, the read head 22r and the write head 22w are arranged in the direction in which the actuator arm 15 extends. The read head 22r is positioned closer to the rotation axis of the actuator arm 15 than the write head 22w.

[0046] In the example shown in Figure 3, when the read head 22r is positioned on a certain data track, the angle θ formed by the arrangement direction of the read head 22r and the write head 22w and the tangent direction of the track to be positioned is non-zero. As a result, the radial position of the read head 22r and the radial position of the write head 22w are different. The distance from the rotation center C of the magnetic disk 11 to the radial position of the read head 22r is defined as r r and the distance from the rotation center C of the magnetic disk 11 to the radial position of the write head 22w is expressed as r w In this case, the radial position of the read head 22r and the radial position of the write head 22w are expressed as L(=|r r -r w Hereinafter, L will be referred to as the distance between head positions.

[0047] The distance between head positions can vary depending on the position of the magnetic head 22. Figure 4 is a diagram for explaining that the distance between head positions in this embodiment varies depending on the position of the magnetic head 22.

[0048] For example, position P a1In this case, the direction in which the write head 22w and the read head 22r are arranged is perpendicular to the radial direction. In this case, the radial position of the read head 22r is the same as the radial position of the write head 22w, so the distance L between the head positions is zero.

[0049] The magnetic head 22 is at position P a1 Area A on the inner periphery inner , for example, when the magnetic head 22 is located at position P a2 3, the write head 22w is positioned more inward than the read head 22r. In other words, the distance L between the head positions is non-zero. The value of the distance L between the head positions is determined by the fact that the position of the magnetic head 22 is at position P a1 The value increases as the distance from the center to the inner periphery increases.

[0050] The magnetic head 22 is at position P a1 Area A on the outer periphery outer , for example, when the magnetic head 22 is located at position P a3 When the magnetic head 22 is positioned at position P, the write head 22w is positioned closer to the outer periphery of the magnetic disk 11 than the read head 22r. In other words, the head position distance L is non-zero. The value of the head position distance L is a1 It increases as it moves away from the outer periphery.

[0051] 3 and 4 are merely examples. For example, the direction in which the write head 22w and the read head 22r are arranged does not have to coincide with the direction in which the actuator arm 15 extends.

[0052] 5 is a diagram for explaining a plurality of measurement positions and a specific measurement position according to the embodiment. In this figure, the area A of the recording surface of the magnetic disk 11 is outer In other words, the write head 22w is positioned closer to the outer periphery of the magnetic disk 11 than the read head 22r.

[0053] Each of the multiple measurement positions is assigned an identification number that increases by one toward the inner periphery. A measurement position with an identification number X (where X is numerical information) is referred to as measurement position #X. Fig. 5 shows 15 measurement positions #0 to #14 as an example of multiple measurement positions.

[0054] Each of the multiple data tracks is assigned an identification number (hereinafter referred to as a data track number) that increases by one toward the inner periphery. A data track with a data track number Y (where Y is numerical information) is represented as a data track DTrk#Y. Figure 5 shows three data tracks DTrk#0 to DTrk#2 as an example of multiple data tracks DTrk.

[0055] As described above, the multiple measurement positions are set regardless of the arrangement of each data track DTrk. Here, as an example, three data tracks DTrk#0 to DTrk#2 are set at intervals of track pitch DTp. Then, 15 measurement positions #0 to #14 are set at intervals of 1 / 4 of the track pitch SvTP of the servo track 41 (i.e., 0.25×SvTP). 0.25×SvTP is different from DTp.

[0056] 5, the radial position of data track DTrk#0 coincides with measurement position #1. The radial position of data track DTrk#1 lies between measurement positions #5 and #6. The radial position of data track DTrk#2 coincides with measurement position #10.

[0057] Hereinafter, the radial position of the read head 22r will be referred to as the read head position.

[0058] In a read operation on data track DTrk#0, a tracking operation is performed so that the read head 22r moves along DTrk#0. That is, the tracking operation is performed so that the read head 22r is maintained above read head position Pr0. The data track DTrk#0 (and read head position Pr0) coincides with measurement position #1. That is, when a read operation on data track DTrk#0 is performed in the read-all process, the RRO correction value can be measured at measurement position #1. Therefore, measurement position #1 is set as a specific measurement position where the RRO correction value is measured in the read-all process.

[0059] In a write operation on the data track DTrk#0, a tracking operation is performed so that the write head 22w moves along the DTrk#0. At this time, the read head 22r is maintained at a radial position (read head position Pw0 in FIG. 5) spaced apart from the DTrk#0 in the ID direction by the head-to-head distance L. For example, when the write head 22w is located at position Pwh on the data track DTrk#0, the read head 22r is located at position Prh, spaced apart from the position Pwh on the data track DTrk#0 in the ID direction by the head-to-head distance L. In the example shown in FIG. 5, the radial position (read head position Pw0) spaced apart from the data track DTrk#0 in the ID direction by the head-to-head distance L coincides with measurement position #4. That is, when a write operation on the data track DTrk#0 is performed in the write-all process, the RRO correction value can be measured at measurement position #4. Therefore, measurement position #4 is set as a specific measurement position where the RRO correction value is measured in the write-all process.

[0060] In a read operation for data track DTrk#1, a tracking operation is performed so that the read head 22r moves along DTrk#1 (read head position Pr1 in FIG. 5). The read head position Pr1 does not coincide with any of the measurement positions.

[0061] In a write operation on data track DTrk#1, a tracking operation is performed so that the write head 22w moves along DTrk#1. At this time, the read head 22r moves to a radial position (read head position Pw1 in FIG. 5) spaced apart from DTrk#1 in the ID direction by the head position distance L. The read head position Pw1 does not coincide with any of the measurement positions.

[0062] In a read operation on data track DTrk#2, a tracking operation is performed so that the read head 22r moves along DTrk#2. That is, the tracking operation is performed so that the read head 22r is maintained at read head position Pr2. The data track DTrk#2 (and read head position Pr2) coincides with measurement position #10. That is, when a read operation on data track DTrk#2 is performed in the read-all process, the RRO correction value can be measured at measurement position #10. Therefore, measurement position #10 is set as a specific measurement position where the RRO correction value is measured in the read-all process.

[0063] In a write operation on data track DTrk#2, a tracking operation is performed so that the write head 22w moves along DTrk#2. At this time, the read head 22r moves to a radial position (read head position Pw2 in FIG. 5) spaced apart from DTrk#2 by the head position distance L in the ID direction. In the example shown in FIG. 5, the read head position Pw2 coincides with measurement position #13. That is, when a write operation on data track DTrk#2 is performed in the write-all process, the RRO correction value can be measured at measurement position #13. Therefore, measurement position #13 is set as a specific measurement position where the RRO correction value is measured in the write-all process.

[0064] In the RRO learning process, SoC30 skips measuring the RRO correction values ​​at specific measurement positions #1, #4, #10, and #13 among measurement positions #0 to #14. Then, SoC30 measures the RRO correction values ​​at measurement positions #4 and #13 in the write-all process. SoC30 measures the RRO correction values ​​at measurement positions #1 and #10 in the read-all process.

[0065] Hereinafter, the group of read head positions during the write operation for each data track DTrk in the write-all process will be referred to as the read-head position group in the write-all process. Similarly, the group of read head positions during the read operation for each data track DTrk in the read-all process will be referred to as the read-head position group in the write-all process. For example, the read-head positions Pw0, Pw1, and Pw2 shown in FIG. 5 are included in the read-head position group in the write-all process. The read-head positions Pr0, Pr1, and Pr2 are included in the read-head position group in the read-all process.

[0066] The multiple measurement positions (e.g., measurement positions #0 to #14) are an example of multiple first positions. A specific measurement position among the multiple measurement positions is an example of a third position. A measurement position among the multiple measurement positions that is different from the specific measurement value (e.g., measurement positions #0, #2, #3, #5 to #9, #11, #12, and #14) is an example of a second measurement position.

[0067] The read head position group in the write-all process and the read head position group in the read-all process are recorded in a read head position table, which is one of the setting information. The read head position table is stored in a predetermined storage area (e.g., FROM 28) in the magnetic disk device 1. The read head position table may be generated outside the magnetic disk device 1 and stored in the predetermined storage area. Alternatively, the SoC 30 may generate the read head position table by itself in some way and store it in the predetermined storage area.

[0068] FIG. 6 is a diagram showing an example of information recorded in the read head position table of the embodiment. As shown in this figure, the read head position table records the correspondence between the data track number and the position of the read head 22r during a read operation and the position of the read head 22r during a write operation. From this figure, it can be seen that the outer circumferential area (area A outer In the area (corresponding to area A), the position of the read head 22r during the write operation is located on the inner side of the circumference than the position of the read head 22r during the read operation. inner ) it can be seen that the position of the read head 22r during a write operation is located on the outer circumferential side of the position of the read head 22r during a read operation.

[0069] For example, in the RRO learning process, the SoC 30 determines, based on the read head position table, whether a certain measurement position matches any of the read head positions in the write-all process or the read-all process. If the measurement position matches any of the read head positions, the SoC 30 determines that the measurement position is a specific measurement position. If the measurement position does not match any of the read head positions, the SoC 30 determines that the measurement position is not a specific measurement position.

[0070] Note that even if the measurement position does not match any of the read head positions in the group of read head positions in the write-all process or the group of read head positions in the read-all process, if a predetermined condition is satisfied, the SoC30 may determine that the measurement position is a specific measurement position. For example, if the distance between a certain measurement position and the closest read head position in the group of read head positions in the write-all process or the group of read head positions in the read-all process is smaller than a threshold value Dth, the SoC30 determines that the measurement position is a specific measurement position. If the distance between a certain measurement position and the closest read head position in the group of read head positions in the write-all process or the group of read head positions in the read-all process is greater than a threshold value Dth, the SoC30 determines that the measurement position is not a specific measurement position. When the distance between a certain measurement position and the read head position group in the write-all process or the read head position group in the read-all process that is closest to the measurement position is equal to the threshold value Dth, the SoC 30 may determine that the measurement position is a specific measurement position, or may determine that the measurement position is not a specific measurement position. The threshold value Dth is, for example, a value equal to or less than the interval between the measurement positions.

[0071] For example, consider a case where the threshold value Dth is equal to the interval between the measurement positions. Because the distances from the read head position Pr1 to the measurement positions #5 and #6 shown in FIG. 5 are both equal to or less than the threshold value Dth, the SoC 30 considers the measurement positions #5 and #6 to be specific measurement positions. Then, the SoC 30 skips measuring the RRO correction values ​​at the measurement positions #5 and #6 in the RRO learning process. When performing a read operation on the data track DTrk#1 in the read-all process, the SoC 30 first measures the RRO correction value at the read head position Pr1. Then, the SoC 30 estimates the RRO correction value at the measurement position #5 by interpolating the RRO correction value at the measurement position #4 and the RRO correction value at the read head position Pr1. The SoC 30 also estimates the RRO correction value at the measurement position #6 by interpolating the RRO correction value at the read head position Pr1 and the RRO correction value at the measurement position #7. In this example, the interpolation is, for example, linear interpolation. SoC 30 may perform second- or higher-order polynomial interpolation.

[0072] In the following description, SoC30 is configured to regard as a specific measurement position a measurement position whose distance from any of the read head positions in the write-all process or the read head position group in the read-all process is less than or equal to a threshold value Dth.

[0073] The threshold value Dth may be 0. When the threshold value Dth is 0, the SoC30 regards only the measurement positions among the plurality of measurement positions that match any of the read head positions in the group of read head positions in the write-all process or the group of read head positions in the read-all process as specific measurement positions.

[0074] Next, the operation of the magnetic disk device 1 according to the embodiment will be described.

[0075] Fig. 7 is a flowchart showing an example of an operation in a manufacturing process executed by the magnetic disk device 1 according to the embodiment. The flowchart in Fig. 7 shows an excerpt of some processes, and processes not shown in Fig. 7, such as adjustment for performing accurate servo control, adjustment for recording user data, adjustment for determining the user data format, a defective servo sector identification process, and a medium defect identification process, may also be performed.

[0076] The SoC 30 executes an RRO learning process (S101). The RRO learning process is executed after the magnetic disk device 1 is assembled and servo data excluding the RRO correction value is written to the servo area SV of the magnetic disk 11. For example, the processor 26 controls a series of operations in the RRO learning process in accordance with a dedicated firmware program.

[0077] After the process of S101, SoC30 executes a write-all process (S102). As described above, in the write-all process, data is written to all data tracks DTrk. Subsequently, SoC30 executes a read-all process (S103). In the read-all process, data is read from all data tracks DTrk.

[0078] Then, the operations in the manufacturing process are completed.

[0079] As described above, after the process of S101, the pair of the process of S102 and the process of S103 may be executed multiple times. The RRO learning process of S101 is an example of a first process. The write-all process of S102 and the read-all process of S103 are an example of a second process.

[0080] FIG. 8 is a flowchart showing an example of the operation of the RRO learning process of the magnetic disk device 1 according to the embodiment.

[0081] First, the SoC 30 initializes a variable X to 0 (S201). X is a variable that can take on a value within the range of the identification numbers assigned to the measurement positions, and is also an index used in the subsequent loop processing. The maximum value of the identification numbers assigned to the measurement positions is set to X max It is written as follows.

[0082] SoC30 determines whether the distance between measurement position #X and the read head position (referred to as the nearest read head position) closest to measurement position #X among the read head positions in the write-all process and the read head positions in the read-all process is equal to or less than a threshold value Dth (S202). SoC30 can identify the nearest read head position based on, for example, a read head position table.

[0083] If the distance between measurement position #X and the nearest read head position is equal to or less than threshold value Dth (S202: Yes), SoC30 stores measurement position #X as a specific measurement position (S203). At this time, SoC30 associates measurement position #X with the nearest read head position and stores them. The storage area in which measurement position #X, which is the specific measurement position, is stored is not limited to a specific storage area. For example, SoC30 stores a pair of measurement position #X, which is the specific measurement position, and the nearest read head position in DRAM29.

[0084] If the distance between measurement position #X and the nearest read head position is not equal to or less than threshold value Dth (S202: No), SoC 30 executes a seek operation to move read head 22r to measurement position #X (S204).

[0085] The SoC 30 acquires a position error signal at the measurement position #X while performing a tracking operation to maintain the read head 22r at the measurement position #X (S205). The position error signal is obtained by demodulating the servo data when the read head 22r passes through the servo area SV. The SoC 30 acquires a position error signal for one rotation of the magnetic disk 11. The position error signal acquired by this process is an example of a first position error signal.

[0086] The SoC 30 calculates the RRO correction value at the measurement position #X based on the position error signal for one rotation of the magnetic disk 11 at the measurement position #X (S206). The SoC 30 calculates the RRO correction value for each servo area SV for one rotation of the magnetic disk 11.

[0087] The SoC 30 stores the RRO correction values ​​for each servo area SV for one rotation of the magnetic disk 11 at the measurement position #X in a nonvolatile storage area (S207). As described above, the nonvolatile storage area to store the RRO correction values ​​may be the servo area SV of the magnetic disk 11, the data area DA, or FROM 28.

[0088] After the process of S203 or S207, SoC30 determines whether X is X max It is determined whether or not it is equal to (S208).

[0089] X is X max If X is not equal to X (S208: No), the SoC 30 increments the value of X by 1 (S209), and the control returns to S202. max If it is equal to (S208: Yes), the RRO learning process is completed.

[0090] FIG. 9 is a flowchart showing an example of the operation of the write-all process of the magnetic disk device 1 according to the embodiment.

[0091] First, the SoC 30 initializes a variable Y to 0 (S301). Y is a variable that can take on a range of values ​​for the data track number, and is also an index used in the subsequent loop processing. The maximum value of the data track number is set to Y max It is written as follows.

[0092] The SoC 30 executes a seek operation to move the write head 22w to the data track DTrk#Y (S302).

[0093] Then, the SoC 30 executes a write operation to write data to the data track DTrk#Y, and stores the position error signal during the write operation (S303).

[0094] In the process of S303, the SoC 30 acquires a position error signal by demodulating the servo data when the read head 22r passes over the servo region SV. Based on the position error signal, the SoC 30 continues the write operation while performing a tracking operation to maintain the write head 22w on the data track DTrk#Y. During the write operation, the SoC 30 stores the position error signal acquired at the read head position for one rotation of the magnetic disk 11. The position at which the position error signal is stored is not limited to a specific position. For example, the SoC 30 stores the position error signal in the DRAM 29. The position error signal acquired by this process is an example of a second position error signal.

[0095] Next, the SoC 30 determines whether the read head position during the write operation on the data track DTrk#Y is associated with a specific measurement position (S304).

[0096] If the read head position during the write operation on the data track DTrk#Y is associated with the specific measurement position (S304: Yes), the SoC 30 calculates the RRO correction value at the read head position (S305). The SoC 30 calculates the RRO correction value in each servo area SV for one rotation of the magnetic disk 11.

[0097] Next, the SoC 30 estimates the RRO correction value at the specific measurement position associated with the read head position by interpolation using the RRO correction value at the read head position during the write operation on the data track DTrk#Y (S306). In the process of S306, the SoC 30 also estimates the RRO correction value in each servo region SV for one rotation of the magnetic disk 11.

[0098] The SoC 30 stores the RRO correction value for each servo area SV for one rotation of the magnetic disk 11 at the specific measurement position in a nonvolatile storage area (S307). As described above, the nonvolatile storage area to store the RRO correction value may be the servo area SV of the magnetic disk 11, the data area DA, or FROM 28.

[0099] If the read head position during the write operation to the data track DTrk#Y is not associated with the specific measurement position (S304: No), or after the process of S307, SoC30 determines that Y is Y max It is determined whether or not it is equal to (S308).

[0100] Y is Y max If Y is not equal to Y (S308: No), the SoC 30 increments the value of Y by 1 (S309), and the control returns to S302. max If it is equal to (S308: Yes), the write all process is completed.

[0101] FIG. 10 is a flowchart showing an example of the operation of the read-all process of the magnetic disk device 1 according to the embodiment.

[0102] First, the SoC 30 initializes a variable k to 0 (S401). Y is a variable that can take on a value within the range of data track numbers, and is also an index used in the subsequent loop processing.

[0103] The SoC 30 executes a seek operation to move the read head 22r to the data track DTrk#Y (S402).

[0104] Then, the SoC 30 executes a read operation to read data from the data track DTrk#Y, and saves the position error signal during the read operation (S403).

[0105] In the process of S403, the SoC 30 acquires a position error signal by demodulating the servo data when the read head 22r passes over the servo area SV. Based on the position error signal, the SoC 30 continues the read operation while performing a tracking operation to keep the read head 22r on the data track DTrk#Y. During the read operation, the SoC 30 stores the acquired position error signal for one rotation of the magnetic disk 11. The position at which the position error signal is stored is not limited to a specific position. For example, the SoC 30 stores the position error signal in the DRAM 29.

[0106] Next, the SoC 30 determines whether the read head position during the read operation on the data track DTrk#Y, that is, the data track DTrk#Y, is associated with a specific measurement position (S404).

[0107] If the read head position during the read operation on the data track DTrk#Y is associated with the specific measurement position (S404: Yes), the SoC 30 calculates the RRO correction value at the read head position (S405). The SoC 30 calculates the RRO correction value in each servo region SV for one rotation of the magnetic disk 11.

[0108] Next, the SoC 30 estimates the RRO correction value at the specific measurement position associated with the read head position by interpolation using the RRO correction value calculated in the process of S405 (S406). In the process of S406, the SoC 30 also estimates the RRO correction value in each servo area SV for one rotation of the magnetic disk 11.

[0109] The SoC 30 stores the RRO correction value for each servo area SV for one rotation of the magnetic disk 11 at the specific measurement position in a nonvolatile storage area (S407). As described above, the nonvolatile storage area to store the RRO correction value may be the servo area SV of the magnetic disk 11, the data area DA, or FROM 28.

[0110] If the read head position during the read operation on the data track DTrk#Y is not associated with the specific measurement position (S404: No), or after the process of S407, the SoC 30 determines that Y is Y max It is determined whether it is equal to (S408).

[0111] Y is Y max If Y is not equal to Y (S408: No), the SoC 30 increments the value of Y by 1 (S409), and the control returns to S402. max If it is equal to (S408: Yes), the read-all process is completed.

[0112] In the positioning in the write-all process (e.g., the processes of S303 to S304 in FIG. 9) and the positioning in the read-all process (e.g., the processes of S403 to S404 in FIG. 10), the SoC 30 uses the RRO correction value measured in the RRO learning process during the seek operation and tracking operation. However, in the RRO learning process, measurement of the RRO correction value at the specific measurement position is skipped. Therefore, in the positioning in the write-all process and the positioning in the read-all process, the SoC 30 may estimate the RRO correction value at the specific measurement position by interpolation and use the estimated RRO correction value.

[0113] FIG. 11 is a diagram for explaining a method for estimating an RRO correction value at a specific measurement position in the write-all process and the read-all process of the magnetic disk device 1 according to the embodiment.

[0114] In the example shown in FIG. 11, in the write-all process or the read-all process, the SoC 30 estimates the RRO correction value of each of the specific measurement positions #1, #4, #10, and #13 by linear interpolation of the RRO correction values ​​at two adjacent measurement positions.

[0115] SoC30 estimates the RRO correction values ​​at measurement positions #4 and #13 using the above method, and uses the estimated RRO correction values ​​in the processes of S303 to S304 in Fig. 9. SoC30 also estimates the RRO correction values ​​at measurement positions #1 and #10 using the above method, and uses the estimated RRO correction values ​​in the processes of S403 to S404 in Fig. 10.

[0116] Then, in the process of measuring the RRO correction value at the specific measurement position (for example, the process of S305 to S306 in FIG. 9 or the process of S405 to S406 in FIG. 10), the SoC 30 updates the RRO correction value at the specific measurement position.

[0117] In this way, by estimating the RRO correction value at the specific measurement position and using the estimated RRO correction value for positioning in the write-all process or the read-all process, it is possible to suppress deterioration in the accuracy of positioning in the write-all process or the read-all process, which is caused by skipping the measurement of the RRO correction value at the specific measurement position in the RRO learning process.

[0118] In the above-described example, the measurement positions are arranged at equal intervals. However, the measurement positions do not necessarily have to be arranged at equal intervals.

[0119] FIG. 12 is a diagram for explaining another example of the arrangement of a plurality of measurement positions according to the embodiment.

[0120] In the example shown in Figure 12, the read head position during write operation is used as the reference position, and measurement positions are located at a position spaced a predetermined distance lpos from the reference position in the ID direction and a position spaced a predetermined distance lpos from the reference position in the OD direction.

[0121] 12, data tracks DTrk#0 to DTrk#2 are arranged at equal intervals as multiple data tracks. Two measurement positions #0 and #1 are set with the read head position Pw10 during a write operation on data track DTrk#0 as the reference position. Two measurement positions #2 and #3 are set with the read head position Pw11 during a write operation on data track DTrk#1 as the reference position. Two measurement positions #4 and #5 are set with the read head position Pw12 during a write operation on data track DTrk#2 as the reference position.

[0122] In a read operation on data track DTrk#0, a tracking operation is performed so that the read head 22r moves along DTrk#0 (read head position Pr10). In a read operation on data track DTrk#1, a tracking operation is performed so that the read head 22r moves along DTrk#1 (read head position Pr11). In a read operation on data track DTrk#2, a tracking operation is performed so that the read head 22r moves along DTrk#2 (read head position Pr12).

[0123] Therefore, the read head positions Pw10, Pw11, and Pw12 are included in the read head position group in the write-all process, and the read head positions Pr10, Pr11, and Pr12 are included in the read head group in the read-all process.

[0124] Here, measurement position #1 coincides with read head position Pr11. Furthermore, measurement position #3 coincides with read head position Pr12. Therefore, SoC30 determines that measurement positions #1 and #3 are specific measurement positions, and skips measuring the RRO correction values ​​at measurement positions #1 and #3 in the RRO learning process. Then, SoC30 measures the RRO correction values ​​at measurement positions #1 and #3 in the read-all process.

[0125] In the example shown in Figure 12, if the distance between a certain measurement position and the read head position closest to that measurement position among the group of read head positions in the write-all process or the group of read head positions in the read-all process is less than or equal to a threshold value Dth, SoC30 may determine that the measurement position is a specific measurement position.

[0126] As described above, according to the embodiment, a plurality of measurement positions are set in the radial direction of the magnetic disk 11. The plurality of measurement positions include a specific measurement position. The SoC 30 executes an RRO learning process (see, for example, S101 in FIG. 7 ). After the RRO learning process, the SoC 30 executes a write-all process and a read-all process (see, for example, S102 and S103 in FIG. 7 ). In the RRO learning process, the SoC 30 measures the RRO correction value at each of the plurality of measurement positions except for the specific measurement position, but does not measure the RRO correction value at the specific measurement position (see, for example, FIG. 8 ). Measuring the RRO correction value at one measurement position includes moving the magnetic head 22 so that the read head 22r is positioned at the measurement position (see, for example, S204 in FIG. 8 ), acquiring a position error signal by the read head 22r while maintaining the read head 22r over the measurement position (see, for example, S205 in FIG. 8 ), and calculating the RRO correction value at the measurement position based on the position error signal (see, for example, S206 in FIG. 8 ). In the write-all process and the read-all process, the SoC30 acquires a position error signal by the read head 22r when accessing a plurality of data tracks (see, for example, S303 in FIG. 9 and S403 in FIG. 10), and calculates an RRO correction value at a specific measurement position based on the position error signal (see, for example, S305 and S306 in FIG. 9 and S405 and S406 in FIG. 10).

[0127] That is, in the RRO learning process, the seek operation of the magnetic head 22 and the tracking operation for one revolution of the data track are omitted for the specific measurement position. Then, in the process after the RRO learning process (the write-all process or the read-all process), the RRO correction value at the specific measurement position is measured during the write or read operation. This reduces the time required to measure the RRO correction value at all measurement positions. In other words, the efficiency of measuring the RRO correction value is improved.

[0128] Furthermore, according to the embodiment, if the distance between the measurement position and the read head position closest to the measurement position among the group of read head positions in the write-all process or the group of read head positions in the read-all process is smaller than a threshold value Dth, SoC30 determines that the measurement position is a specific measurement position.If the distance between the measurement position and the read head position closest to the measurement position among the group of read head positions in the write-all process or the group of read head positions in the read-all process is larger than a threshold value Dth, SoC30 determines that the measurement position is not a specific measurement position.

[0129] According to the embodiment, when accessing one of the multiple data tracks in the write-all process or the read-all process, the SoC30 calculates an RRO correction value at the specific measurement position based on a position error signal acquired from a read head position that is closest to the specific measurement position among the read head positions in the write-all process or the read head positions in the read-all process (see, for example, S303 to S306 in FIG. 9 and S403 to S406 in FIG. 10).

[0130] This reduces the time required to measure the RRO correction values ​​at all measurement positions, thereby improving the efficiency of measuring the RRO correction values.

[0131] According to the embodiment, the SoC 30 determines the specific measurement position based on a read head position table that is information recording the read head positions in the write-all process and the read-all process.

[0132] The method for determining the specific measurement position is not limited to the method using the read head position table. When the intervals between the multiple measurement positions are uniform, the SoC30 may divide numerical information indicating the read head positions of the read head position group in the write-all process and the read head position group in the read-all process by the intervals between the measurement positions, and determine the specific measurement position based on the value obtained by the division.

[0133] According to the embodiment, the SoC 30 estimates the RRO correction value at the specific measurement position using the RRO correction values ​​at at least two measurement positions other than the specific measurement position, and then, in a write operation or a read operation to multiple data tracks in a write-all process or a read-all process, the SoC 30 positions the magnetic head 22 using the estimated RRO correction value.

[0134] Therefore, it is possible to suppress deterioration of positioning accuracy in the write-all process or the read-all process due to skipping measurement of the RRO correction value at a specific measurement position in the RRO learning process.

[0135] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0136] 1 magnetic disk drive, 2 host, 11 magnetic disk, 12 SPM, 13 ramp, 15 actuator arm, 16 VCM, 22 magnetic head, 22r read head, 22w write head, 24 preamplifier, 25 RWC, 26 processor, 28 FROM, 29 DRAM, 41 servo track.

Claims

1. a magnetic disk having a plurality of tracks, the magnetic disk having first positions set in a radial direction for measuring a plurality of RRO (Repeatable Run Out) correction values, the first positions including a plurality of second positions and a third position different from the second positions; a magnetic head including a write head for making write access to the magnetic disk and a read head for making read access to the magnetic disk; performing a first step of measuring an RRO correction value at each of the plurality of second positions and not measuring an RRO correction value at the third position, wherein measuring the RRO correction value at each of the plurality of second positions includes: moving the magnetic head so that the read head is positioned at a fourth position, which is one of the plurality of second positions; obtaining a first position error signal by the read head while maintaining the read head over the fourth position; and calculating an RRO correction value at the fourth position based on the first position error signal; After the first step, a second step is executed to perform the write or read access to the plurality of tracks, the second step including: acquiring a second position error signal by the read head during the access; and calculating an RRO correction value at the third position based on the second position error signal. A controller; A magnetic disk device comprising:

2. The controller determining that a first position among the plurality of first positions, the distance to a nearest fifth position among a plurality of fifth positions being the position of the read head when accessing one of the plurality of tracks, is greater than a threshold value, is one of the plurality of second positions; a first position among the plurality of first positions, the distance of which to a nearest fifth position among the plurality of fifth positions is smaller than the threshold value, is determined to be the third position; 2. The magnetic disk drive according to claim 1.

3. the second position error signal is a position error signal acquired from a sixth position when accessing one of the plurality of tracks in the second step, the sixth position is a fifth position among the plurality of fifth positions that is closest to the third position; 3. The magnetic disk drive according to claim 2.

4. the controller determines the plurality of second positions and the third position based on information recording the plurality of fifth positions; 3. The magnetic disk drive according to claim 2.

5. the controller estimates an RRO correction value at the third position using RRO correction values ​​at at least two of the plurality of second positions, and positions the magnetic head using the estimated RRO correction value at the third position during the access in the second step.

5. The magnetic disk drive according to claim 1.

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